Carbon fiber-reinforced polymers (CFRPs) are composite materials including carbon fibers as reinforcing agents bound in a matrix, typically a matrix of a plastic composition. CFRPs are used in a variety of consumer and industrial products. A high cost of virgin carbon fibers of industrial or commercial grade limits utilization in a broader-range of end-user applications, including limiting broader use in automotive and transportation sectors where there is significant potential for expanded use.
Even with the high cost of virgin carbon fibers, a significant quantity of CFRPs, and the carbon fibers therein, end up as waste. It is common in CFRP applications for material trim and scrap waste to amount to about 30% or more of finished part weight. This waste is often incinerated or sent to a landfill resulting in additional waste disposal costs and significant lost raw material value.
Such trim and scrap waste represent a possible resource for recycled carbon fibers, and attempts have been made to process such trim and scrap waste to recover carbon fibers for recycle. However, effectively freeing carbon fibers for recovery from CFRP matrix has proven difficult, with a result being that recycle processing has tended to be expensive and/or to result in significant degradation of carbon fiber properties, significantly limiting utility of recycling as a source of carbon fibers for a range of possible applications.
One CFRP recycling technique involves subjecting waste CFRP to pyrolysis. This technique utilizes high temperatures to decompose polymeric matrix while attempting to leave the reinforcing fibers intact. The carbon fibers recovered from this processing often have a short fiber length with limited potential for reuse in new products. Also, pyrolysis, as a process option, has significant limitations with respect to intensive energy requirements, high processing costs, and potential for negative environmental impact due to emission of pyrolysis by-products.
Another type of CFRP recycling technique uses chemical agents to chemically react with and degrade, and break down the polymeric matrix (sometimes referred to as depolymerization) to degradation products that may be separated from the carbon fibers, such as by dissolution of the degradation products into a solvent. Such processes tend to be expensive and may also degrade carbon fiber properties.
A need exists for improved processes to recover carbon fibers from CFRP waste for recycle in a manner that increases the range of applications in which recycled carbon fibers may be technically and economically suitable for use.